Alexander, ----- Original Message ----- From: "Varshavchick Alexander" <[EMAIL PROTECTED]> To: "'Heikki Tuuri'" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Friday, September 06, 2002 10:08 AM Subject: RE: Performance Problems with InnoDB Row Level Locking...
> Hi Heikki, > > one more question please about innodb_flush_log_at_trx_commit: if there > was some way of increasing the delay between log flushes more than 1 sec, > can you estimate will it bring any real effect in performance? I know > it'll raise the risk of losing some last transactions if something > crashes, but we can go for it gaining the speed. How can it be done if > it's worth doing? it should not be worth doing. A disk can do some 70 random writes per second, and the log flush (calling fsync on the log file) typically uses 2 disk writes: (1) writing the end of the log to the log file on disk, and (2) updating the file access timestamps in the 'inode' of the file, if we are using a Unix file system. Thus the performance benefit of less than 1 log flush per second is small. On the other hand, we might add an option which allows flushing the log 1 - 50 times per second. Note that the file flush method fdatasync is supposed to eliminate the write (2) above. Unfortunately there was evidence fadatasync caused file corruption in Linux and Solaris, and it is currently mapped to the ordinary fsync. > Thanks > > sql, query > ---- > Alexander Varshavchick, Metrocom Joint Stock Company > Phone: (812)118-3322, 118-3115(fax) Best regards, Heikki Tuuri Innobase Oy --- InnoDB - transactions, hot backup, and foreign key support for MySQL See http://www.innodb.com, download MySQL-Max from http://www.mysql.com --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
